146:. A large number of cylinders and often the need for reduction gears and supercharger drives made it impractical to manufacture a one-piece crankshaft, so Hirth joints were used to couple the sections. They have been used in complex crankshafts for many years afterward, particularly where the output power was taken from a central drive gear. As a large gear could neither be formed-in-place nor passed over the crank webs, it could be machined separately and placed between two half-crankshafts with Hirth's joints. They are also used in
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The teeth mesh around a ring, as the torque capacity of teeth increases with their diameter. This ring is arranged to be at the maximal possible diameter for the space available. The centre of a shaft is not toothed, as this would add little torque capacity to the coupling and the increasingly narrow
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The coupling is defined by the groove count, the outer diameter of the cylindrical feature, the bottom angle of the grooves (to the axis of the cylindrical feature), and their depth. Hirth joints are designed as mating pairs and, unlike splines, there is no standardised off-the-shelf sizing system
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Curvic couplings are similar in concept and appearance to Hirth couplings, except that their teeth are curved instead of straight. Like Hirth couplings, they lock the components together in an unlockable/removable way and provide
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into the end face of a rotary component such as a shaft or the hub of a wheel. Two such components with matching splines are held together by a bolt through the middle, and coupled without compromising the torque capacity.
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by simply applying an axial load. This is done by either bolting the shafts together or by applying spring pressure from an external housing. This lack of backlash also reduces wear due to
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For instance, a shaft of 60 mm diameter can be toothed in a 12 mm wide ring only (inner diameter is 36 mm) without jeopardizing the load-bearing capacity of the shaft.
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The crank design and technology was licensed from
Lightning Cycle Dynamics, which utilized and patented a two-piece bicycle crank using the Hirth coupling in 1995.
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are used to couple two rotary components axially. The coupling is compact, self-centering and has a high torque capacity. It was developed by
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shafts, in accessories for surgical operating tables, in agricultural machines for fixing tools etc., and in bike parts and frames, such as
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and rotary tables for precision machining and inspection tasks. Commercial products such as the
Ultradex achieve sub-arc-second accuracy.
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Large-diameter Hirth couplings can effect extremely accurate and repeatable rotational positioning. For this reason, they are used in
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Very high loads can be transferred in a small enclosure of only a few parts (two serrated faces and a bolt fixing them together).
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Specialized's "S-Works" top-level racing mountain bike cranksets use a Hirth joint with a center
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Hirth-like joints are often found on camera support equipment, where they are called rosettes.
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The joint is self-centering (because of this the Hirth coupling is used in very high RPM
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of 60 and 90 degrees are used. A key feature of the Hirth joint is that, unlike simple
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Hirth joint (disassembled) between the semi-axles of a
Campagnolo Ultra-Torque crankset
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The manufacturing process is complex, time-consuming and consequently expensive.
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wear resulting in looseness, tightening the fixing bolt can restore firmness.
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42:, an engine manufacturer in Germany, and so is often also referred to as a
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Hirth joint made from anodized aluminum to show the meshing of the teeth
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169:-head threaded rod to secure the crank halves together.
142:Hirth's joints were first used in aircraft engine
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77:Tapered, symmetrical serrations are used.
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229:The High-Speed Two-Stroke Petrol Engine
71:teeth would become impractical to cut.
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58:Face splines consist of radial teeth
231:. London: Foulis. pp. 381–382.
318:"Wooden Camera Rosette Gear Review"
50:particularly in German literature.
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273:"Specialized Bicycle Components"
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109:There is no lag in the joint.
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16:Type of mechanical connection
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154:'s "Ultra-Torque" bicycle
350:Rotating shaft couplings
298:"Ultradex Rotary Tables"
253:"Cranks -- Center Clamp"
160:Bicycle Torque Couplings
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320:. 20 February 2014.
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335:Elastic Averaging
119:If there is some
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275:. Archived from
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225:Smith, Philip H.
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205:Rotating spline
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186:Curvic coupling
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329:External links
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177:indexing heads
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79:Profile angles
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48:Hirth coupling
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279:on 2013-05-21
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128:Disadvantages
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301:. Retrieved
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281:. Retrieved
277:the original
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256:. Retrieved
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238:085429-049-4
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193:indexability
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114:gas turbines
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54:Construction
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40:Albert Hirth
36:Face splines
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148:gas turbine
144:crankshafts
44:Hirth joint
303:2013-09-26
283:2013-06-25
258:2007-04-27
211:References
152:Campagnolo
101:Advantages
97:for them.
158:, and in
344:Category
227:(1965).
199:See also
156:crankset
121:fretting
91:fretting
87:backlash
83:splines
235:
64:ground
60:milled
233:ISBN
138:Uses
167:hex
62:or
46:or
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116:).
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
